Compositions containing leuco xanthene dyes and suitable activators



United States Patent COMPOSITIONS CONTAINTNG LEUCO XAN- THENE DYES ANDSUHTABLE ATHVATORS Robert H. Sprague, Chagrin Falls, John A. Stewart,

Parma, and James M. Lewis, Cleveland, Ohio, assignors to HorizonsIncorporated, Cleveland, Ohio, a corporation of New Jersey No Drawing.Filed Apr. 17, 1963, Ser. No. 273,569

7 Claims. (Cl. 96-90) This invention relates to non-silverphotosensitive compositions which print-out an image directly uponexposure to a suitable dosage of visible light, and to the use to suchcompositions as thin films in photographic processes. More particularlythis invention relates to photosensitive compositions comprising atleast one colorless leuco compound which when intimately admixed withone or more colorless activator compounds, yields a mixture which whenexposed to visible light prints out a visible image directly, at speedswhich are of practical significance, and to the processing of suchcompositions to yield a permanent useful image.

(1) THE LEUCO COMPOUNDS The leuco compounds which may be utilized inaccordance with the present invention comprise two recognized classes ofdye forming colorless compounds which are generally similar to the leucotriarylrnethane dyes except that they are characterized by the presenceof one or more bridging hetero atoms and therefore are compounds whichmaybe represented by the general formulas wherein each R is selectedfrom the group consisting of H, lower alkyl and aryl and may be the sameor different and R is selected from the group consisting of H, alkyl andaryl, including particularly and and wherein Z represents a memberselected from the group consisting of 0, 8, Se and NH.

As indicated, the preferred leuco compounds of this class aresubstituted in the 3,=6-positions and include 3,6 bis dimethylamino-9-(p-dirnethylaminophenyl xanthene 3,6-bis( diethylamino -9-(p-dimethylaminophenyl xanthene 3,272,635 Patented Sept. 13, 1966 3,6bis (diethylamino -9-(p-diethylaminophenyl) xanthene 3, 6 bisdimethylamino) -9- (p-dimethylarninophenyl thioxanthene (2) THEACTIVATORS A diverse group of colorless C:O containing organic compoundshave been found to be useful in the present invention. These compoundsmay be grouped as follows:

1) Carboxylic acids represented by the general formula wherein R isselected from the group consisting of H, alkyl, aralkyl, aryl, and

R being selected from the group consisting of H, alkyl, aralkyl andaryl;

(3) Cyclic keto compounds represented by the general formula where Qrepresent-s the non-metallic atoms necessary to complete a tfiveorsiX-rnembered heterocyclic ring and wherein the -ke-to oxygen isattached to a ring carbon in said ring.

(3) EVALUATION PROCEDURE The data reported in the tables which ifollowis the result of tests establishing the effect of visible light onmixtures of various activator compounds with the indicated leuco bases.In general one of three procedures was followed.

In the first two, a mixture is prepared consisting of equal parts byvolume of acetone and a 10% solution of polystyrene in benzene, 2 cc. ofeach being used in most instances. Then the indicated weights of theleuco compound and of the activator were dissolved in the mixture. Theresulting composition formed from originally colorless materials had acloudy or hazy appearance or a faint pinkish color in most instances.The composition was coated by means of a Bird applicator on SOOHD Mylarin a coating having an 0.0015 inch wet thickness and the coating waspermitted to dry in air. Thereafter the composition was exposed eitherto a photoilood lamp through a step tablet or on an Eastman Kodaksensitometer with a suitable filter.

the use of a 78AA filter, to equal mean noon-day light.

The resulting image was fixed by a solvent wash or by exposure to heat.Thereafter the density of the image was read and the LES. was computedas described below.

-In a third procedure, the polystyrene was omitted from the compositionsand instead a mixture of benzene and acetone was used as the solvent forthe indicated amounts of the leuco compound and the activator. Thesolution was poured onto filter paper and the photosensitive materialwas then exposed through an Eastman No. 2 Step Tablet to one GeneralElectric Refiector Photoflood lamp for 30 seconds at a distance of 12inches from the lamp to the sensitive material. The densities of theresulting step wedge were read on an Eastman No. 1 color densitometerthrough the green filter.

L.E.S. (abbreviation for light exposure speed) refers to a speed ratingsystem developed at the Wright Air Development Division of Air Researchand Development Command (USAF), and is defined as the reciprocal of theexposure in meter candle seconds which is required to produce a doublediffuse reflection density of 0.2 density units above base plus fog. Asin the more conventional ASA system used to rate silver halide films,the higher the LES number the faster the film is.

Compositions consisting of the indicated weight of 3,6-bis-(dimethylamino) -9 (p-dimethylaminophenyl)xanthene (hereinafteridentified as D-l79), and the indicated Weight of the specifiedactivator dissolved in a mixture of acetone and 2 cc. of a 10% solutionof polystyrene in benzene coated 0.0015-inch wet thickness on Mylar andair-dried were exposed using an Eastman No. 101 sensitometer for theindicated time with the light converted by the use of 8. 78AA Eastmanfilter to equal mean noonday light or to one General Electric No. 2Reflector Photofiood lamp (RFL2), at a distance of 12 inches. An EastmanKodak No. 2 Step Tablet was used to print a step tablet. The exposedmaterial was stabilized by two or more successive rinses in a mixture of1 part acetone and 4 parts petroleum ether, or by being maintained at125 C. in a convectiontype oven for four (4) minutes. The stabilizedmaterial was reexposed for 5 minutes to the RFLZ with no darkening. Thedensities in the resulting step wedge were read with an Eastman No. 1color densitometer using the green filter, the results for thephotoflood exposures are reported in Table I and the densitometerexposures in Table II.

Table I Densities, RFLZ Weight, Type 01 Exp. No. 01 No. Activators UsedWith D-179 mg. Fixing Min. Steps Gross Base Net Fog i ffffi jjr"1111;311:1311: "i 5 19 Q36 2 .1 Ia-Naphthoie Aci 5 21 1.57 0.25 1.32D-179 5 21 2. 57 0. as 2. 24 3 g Acld I 5 21 2.12 0. 25 1,37

5 21 2.02 0.23 1.79 5 18 1.85 0.34 1.51 -179 5 21 1. 45 0. 25 1, 20 7 lgf egl f f fff f 5 21 2. oo 0.15 1,85 8 2,4-Diehlorophenoxyaeetic Aeid, 521 2. 60 0. 29 2. 31 9 {is tt fffi'iit ffffith'itfiiit? 5 21 w w {g q qs 2 21 a. 00 0. 21 2, 79 11 igfi t ro e 5 8 0.48 0.23 0.20

D 1'%8fX f iT i?:::: 5 11 M4 13 {(113 ,$Tr1ehloroacetan1hde 5 11 L [L28L02 14 l-Aeeto-Z-naphthol 5 21 1.77 0.78 0.99 15 lg-1Z9. t Ta 5 21 1.310. 30 1.01 gg e e 5 12 0.87 0.28 0,59 {152 i? 5 12 1,61 0. 20 1, 4 {ggtgg f- 5 10 1.19 0.32 .187 18 Acetoacet-2,5-dichlor0-N-benzoyla1ilidef"-1 5 6 0.77 0.48 0.29 19 1I 3c e1t7gaeet- 2,5-d1chloro-N-(m-nltroenz0y)an11de 5 9 0'60 016 0. 44 23223it???lfiii ffiifififtifl itz:: 5 180.18 2.18 21 {hjioii ltg-Benzoyl Aeeto-4,3,3-dichl0robenzidide- 5 12 L160' 44 0' 72 D 1 5 17 1. 77 0.24 1. 53 t i liz g t y t t i g 2g 0. 35 9025. rhenifiimimw 0.13 1. as 9 5 11 2.20 0.17 2. 03 26.-. 3-M Ll l-ll ll11-57911Rfiiiffffifi? 5 14 27 1,3-Diphenyl-5-pyrazolone. 5 1 r 28Benzothiazolone 1 0 50 D 17g 5 12 2. 32 0. 1. 87

FIXING Two distinct methods of fixing or stabilizing the colored imageproduced have been described. In the one the exposed material issubjected to two or more second rinses with a suitable solvent and inthe other the exposed material is subjected to mild heat (125) for about4 minutes. The method of stabilization selected in any specific instancewill depend to some extent upon the materials being used and it is to benoted that many of the slower compositions may be preferable to some ofthe faster compositions because some of the latter are less susceptibleto heat or dry fixing than some of the former.

While not wishing to be bound by any specific theory as to the manner inwhich the exposure to visible light to an initimate mixture comprisingtwo or more originally colorless compounds produced a colored image, itis believed that the final colored image which forms in the light struckareas is always the dye which forms as a result of oxidation of theleuco base. Furthermore it appears that when the photosensitive mixtureis prepared, on

mixing the compounds which are colorless, a weakly tinted mixture isformed.

It is also considered possible that the real active ingredient in themixture is that very minute amount of an oxidized product which resultswhen the leuco base is exposed to oxygen e.g. in the ordinaryatmosphere.

Whatever the true mechanism each of the activators listed above, ormixtures of the same, bring about oxidation of the leuco compound uponexposure to a suitable dose of visible light and as a result form adirect visible print-out image in the light struck areas.

PROPORTIONS The relative proportions of the leuco dye bases and theactivators for the same may be varied considerably from the weightproportions given by way of illustration in the examples and arepreferably within the range between 10 to 1 and l to 10 parts by weight.

As with other photosensitive compositions if not used at the time theyare prepared the compositions of the present invention would be storedin cool dark relatively dry surroundings.

Having now described the invention in accordance with the patentstatutes it is not intended that it be limited except as may be requiredby the appended claims.

We claim:

1. A composition which prints out a visible image directly as a resultof exposure to visible light said composition comprising an initimatemixture consisting essentially of (1) at least one leuco compoundselected from the group consisting of leuco compounds represented by oneof the following general formulas wherein each R is selected from thegroup consisting of H, lower alkyl and aryl and not all of the Rs needbe the same and wherein R is selected from the group consisting of H,lower alkyl and aryl and Z is selected from O, S, Se and -NH:

R\ Z /R R R 1';

and wherein each R has the same meaning as indicated above and Zrepresents a member selected from the .group consisting of O, S, Se and-NH', and (2) at least one colorless non-toxic C=O containing organiccompound selected from the group consisting of (a) carboxylic acidsrepresented by the general formula RCOOH wherein R is selected from thegroup consisting of aryl and alkaryl (b) acyclic keto compoundsrepresented by the general formula wherein R" is selected from the groupconsisting of aryl,

I NH-aryl and i i" C H:C Nary1 wherein R is selected from the groupconsisting of H, alkyl, aralkyl, aryl and II "C I Rb R being selectedfrom the group consisting of H, alkyl, aralkyl and aryl; and A isselected from the group consisting of alkyl, alkaryl and aryl and (c)cyclic keto compounds represented by the general formula 1 wherein Qrepresents the non-metallic atoms necessary to complete a heter-ocyclicring with at least 5 and not more than 6 atoms in the ring and whereinthe keto oxygen is attached to a ring carbon atom is said ring;

said compounds being present in the mixture in proportions rangingbetween 1:10 and 10:1 relative to each other,

by weight.

2. The composition of claim 1 wherein the leuco compound is a xanthene.

3. The composition of claim 2 wherein the leuco compound is a 3,6bis(dialkylamino) 9 (p dialkylaminophenyl)xant-hene.

4. A dry film consisting of the composition of claim 1 dispersed in athin layer on an inert support.

5. The film of claim 4 wherein the support is a film forming plastic.

6. The film of claim 4 wherein the mixture is supported by a cellulosecompound selected from the group consisting of cellulose and filmforming cellulose derivatives.

7. The film of claim 4 wherein the support is transparent.

References Cited by the Examiner UNITED STATES PATENTS NORMAN G.TORCHIN, Primary Examiner.

10 D. D. PRICE, Assistant Examiner.

1. A COMPOSITION WHICH PRINTS OUT A VISIBLE IMAGE DIRECTLY AS A RESULTOF EXPOSURE TO VISIBLE LIGHT SAID COMPOSITION COMPRISING AN INTIMATEMIXTURE CONSISTING ESSENTIALLY OF (1) AT LEAST ONE LEUCO COMPOUNDSELECTED FROM THE GROUP CONSISTING OF LEUCO COMPOUNDS REPRESENTED BY ONEOF THE FOLLOWING GENERAL FORMULAS